1. Field of the Invention
This invention relates generally to communication systems, and, more particularly, to wireless communication systems.
2. Description of the Related Art
Conventional wireless communication systems use a network of base stations or other access points to provide wireless connectivity to one or more mobile units. A mobile unit and the base station may establish communication over a wireless communication link or air interface. The wireless communication link may be used to exchange information such as voice packets exchanged by the mobile unit and another user in the wireless communication system. The channel conditions over the wireless communication link typically vary due to a wide variety of factors including changes in environmental conditions, movement of the mobile unit, interference with other radiofrequency transmissions or noise, and the like. In some cases, the channel conditions can deteriorate to such an extent that the wireless communication link is no longer able to carry voice packets or other information. Since the mobile units at either end of the call are not receiving voice packets, they render silence over the speakers or earphones of the mobile unit. Users of the mobile units are therefore unable to determine whether or not silences occur because another user has stopped speaking or because the channel quality has deteriorated.
Calls over wireless communication links may be dropped when the channel quality of the wireless communication link remains too low to support communication for a selected period of time. Calls may also be dropped for a other reasons that are not necessarily related to channel quality. For example, a call may be dropped due to a failure in the network signaling sequence during a handover or other mobility-related event. The wireless communication systems and the mobile units may clear the dropped call so that one of the users must manually re-establish the call (e.g., by redialing the other user) if the user wishes to continue the call. This approach has a number of disadvantages. For example, the parties in the call cannot determine whether the call was dropped because of poor channel conditions or because the other user intentionally terminated the call. For another example, redialing the call is tedious and may cause user frustration, particularly if one of the users is in a region with relatively weak coverage and the call is repeatedly dropped. For yet another example, neither of the parties in the call will know whether we should attempt to redial the other party or whether they should await a redial attempt from the other party when a call is dropped. This may lead to a delay in reestablishing the call, a collision between incoming and outgoing calls (which may in turn lead to one or both parties being directed to the other party's voicemail box), or other undesirable complications.